Failure to thrive is a disorder where infants and children do not gain weight or may lose weight at an expected rate. It is defined as weight being below the 3rd percentile on a growth chart or weight gain less than 20g/day from birth to 3 months or 15g/day from 3-6 months. Failure to thrive can be organic due to medical causes, inorganic due to non-medical causes like poor parenting, or mixed. Causes include inadequate calorie intake, absorption issues, increased calorie needs, excessive calorie loss, or altered growth regulation. Assessment involves a physical exam, growth chart, and lab tests. Management focuses on correcting underlying issues, improving nutrition and caregiving, and follow up to support catch